Temperature control system



March 15, 1932. I c. WILHJELM ET AL 1,849,162

. TEMPERATURE CONTROL SYSTEM Filed June 131 1930 INVENTORS.

9am. r: 734

A TTORNE Y.

' normal temperature Patented Mar. 15, 1932 UNITED STATES PATENT OFFICE CHRISTIAN WILHJ'ELM, OF PHILADELPHIA, PENNSYLVANIA, AND GLENN S. FBAZEE, OI CLEVELAND, OHIO; SAID FRAZEE ASSIGNOR TO SAID WILHJ'ELM TEMPERATURE CONTROL SYSTEM Application filed. June 13, 1930. Serial No. 460,977.

In the art which relates to the regulation and control of the temperatures in furnaces and ovens it has been found that a lar e number of them require a far greater vo ume of fuel for merely heating up or starting purposes than for purposes of regulation and after the normal working temperature has been reached. 7

In some cases the temperature control system merely opens or closes a fuel supply valve in order to increase or decrease the supply by given quantities in response to a decrease or increase in the temperature in a furnace or oven. If the variations in'the fuel supply are large, there will be correspondingly large very undesirable fluctuations in the temperatures. And if, in addition, it is required that there be a supply of fuel sufiicient to start the furnace without manually adjusting the maximum supply required for this purpose, it is obvious that when there is a decrease in temperature, there will be supplied a far greater quantity of fuel than is required for regulation in response to the variations or such as may be expected under the circumstances.

It has been proposed to avoid this objectionable feature by providing a by-pass valve in addition to the regular fuel supply control valve, and start the furnace with fuel passing through both valves and then closing the by-pass valve when the temperature reaches the desired point or gets close to it. This arrangement includes the disadvantage of dependin upon an operator to be present to close the y-pass valve in time in order to avoid an excess supply of fuel.

If the operator neglects his duties or for some reason is unable to attend to them, the by-pass valve is of no use or benefit but rather a disadvantage which may or may not cause serious trouble.

The object of this invention is to provide an improved temperature control apparatus including a by-pass valve and means for closing it automatically to eliminate troubles due to manual operation. invention is to provide means for regulating the temperature fuel supply is closed down ahead of time or ed at 15 on a suitable also operates Another object of the in such a manner that the p soon enough to prevent or eliminate overshooting of the temperature in a'furnace or oven.

Still another object of the invention is to provide an apparatus for the aforesaid purposes which shall be simple and eflicient in construction and operation.

The invention may be embodied in apparatus of many different forms, designs and constructions and we do not wish to limit ourselves to any particular form. We have, however, embodied our invention in a very simple apparatus and illustrated it diagrammatically in the accompanying drawing.

In the drawing the reference numeral 1 denotes a furnace which is heated by fuel supplied to a nozzle 2, for instance, through a fuel supply pipe 3. The fuel supply is controlled by a regulating valve 4 and there is also provided a by-pass 5 controlled by the by-pass valve 6. 7 and 8 are valve operating levers which may be adjusted or set by any well known adjusting means indicate 9. The two valve arms 7 and 8 are connected by a link 10. Arm 7 is pivoted to the link at 11 whereas arm 8 is connected'bya pin 12 moving in a slot 13 in the link. The length of the slot is substantially or practically equal to the throw of the by-pass valve from open 'to closed positions.

The link 10 is operated by a lever 14 pivotbase 16 which supports the operating mechanisms. The lever is oscillated by a connecting rod 17 from a crank disk 18 driven by sui ble gearing 19 from a reversible motor 20. The connecting rod 17 a limit switch 21 which opens and closes the electric circuits for operating the motor to which current is supplied from the main line supply wires 22 and 23.

Let us now assume that the furnace is provided with a temperature indicating device for closing a circuit through the motor where by the valves are opened'when the temperature decreases in the furnace and vice versa. The operation will then be as follows.

Tostart the furnace both valves will be opened with the arms 7 and 8 in the dotted ositions, and the furnace will be supplied with fuel both through the main line 3 as well as through the by-pass 5, which latter supplies the additional volume of fuel necessary to raise the temperature to the working or normal degree required for the work to be done.

When the working temperature has been reached, the temperature indicating device, which we assume has been provided, will respond to the temperature increase and close a circuit through the motor which will cause the latter to actuate the elements 19-1817 and 14 to move the link 10 to close the valves at which time the valve arms 7 and 8 will be in the positions shown in full lines.

Consequently the by-pass valve 6 will be fully closed and the control valve 4 will be closed to permit the minimum required fuel gupply to pass through the main fuel supply ine 3.

If now the temperature in the furnace varies so as to require a change in the fuel supply, the temperature indicating device will in the usual manner open and close circuits to the motor to cause the main valve to be operated accordingly, and without in any manner whatsoever operating the by-pass valve, because whenever the link 10 is operated, it will slide idly on the by-pass valve operating arm 8.

The mechanism thus far disclosed permits opening of both valves to start the furnace; closing of both valves when the desired normal temperature has been reached and operations of the main valve in response to temperature changes within the furnace without operating the by-pass valve so that the disadvantages accompanying manual closing of the bypass have been eliminated.

ome furnaces, however, require such a large quantity of additional or excess fuel to heat up to normal temperature that the mere closing of the by-pass valve, when the normal temperature is reached, is insufficient to prevent a rise in temperature far above the normal. It therefore becomes necessary or desirable to provide means for closing the bypass valve and the main control valve ahead of time and our invention provides an apparatus for accomplishing this purpose.

Referring now again to the drawing, the reference numeral 25 denotes a gas filled bulb inserted in the.furnace and connected to a helical tube 26 which in turn is connected in any well known manner to a pointer 27. As the temperature rises or falls in the furnace, the helical tube expands or contracts and in turn operates the pointer which indicates the variations in temperature on a suitable scale 28. Such a mechanism is well known in the art.

The pointer 27 swings around a pivot 29. On the latter is also pivoted a contact arm 30 having an abutment 31 and a contact 32. There is second contact arm 33, also pivoted at 29, and provided with an adjusting screw 34 and a contact 35. 36 is a spring which tends to pull the contact arms 30 and 33 together. v 37 is a small magnet, permanent or electromagnet, which attracts an armature 38 on the contact arm 33. The magnet is adapted to be clamped in a given position along or on the track 39. The magnet carries an indicator 40.

The contact arm 30'is connected by a wire 42 to one side of the limit switch 21. The other contact arm 33 is connected to the other side by a wire 44, while the pointer 27 is connected by a wire 46 to the line 22. The pivot 29 is a friction pivot of any suitable construction so arranged that if arm 33 is set in a certain position, it remains in that position even if the other arm 30 is moved away from 33 and the spring 36 is tensed. The spring tends to keep the two contact arms 30 and 33 together if the pointer 27 does not separate them by its movements in accordance with the temperature changes. The adjusting screw 34 sets the limit of the closing or coming together movement of the two arms 30 and 33.

The operation is as follows: When the fur- .nace is cold, pointer 27 stands at zero in contact with the arm 30 because of the spring 36, while at the same time contact arm 33 is set. say at 750 which is the point at which it 1:: desired to close the by-pass valve 6 before the temperature reaches normal which in this case, is say 800, at which point the magnet indicator 40 is set.

Now the'furnace is lit and the line closed whereby a motor circuit is established as follows. From line 22 to wire 46, to pointer 27, contact 32, arm 30, wire 42 to limit switch 21 to the motor and back to line 23. The motor therefore starts and opens the valve 4 fully to supply fuel to the furnace through the main line 3, while the by-pass valve 6 is free to be manually operated to supply additional fuel to bring the furnace temperature up to the desired point at maximum rate.

As the temperature rises, the pointer 27 and contact arm 30 will move upwards on the drawing until when the temperature reaches 750 or slightly before, the contact arm abutment 31 engages the screw 34 and the arm 30 stops moving. The temperature, however, continues to rise in the furnace so pointer 27 continues its movement until it reaches the other contact arm 33 and another motor circuit is made at 35 as follows From line 22 to wire 46, to 27, 35, wire 44 to the other side of limit switch 21, which is now closed, to the motor and back to the line. The motor starts again but in the reverse direction and moves the valves into closed positions. Thus the fuel supply is cut down when the temperature is 50 away from the normal point, overshooting is prevented and the temperature will drift, as it were, and

slowly rise towards the 800 mark. During two contact arms form the two extreme limits between which the pointer 27 may move.

in response to the temperature. changes in the oven, making contacts at 32 and 35 to close circuits through the motor to open or close the main valve 4.

It will therefore be seen, that this invention provides an apparatus whereby the main control valve is opened at the start and both valves closed ahead of time, and that thereafter the apparatus is operated to set the extreme limits within which the motor is again operated to open or close the main valve without operating the by-pass valve. It will also be noted that adequate adjusting means have been provided.

The invention may be embodied in other forms and different types of standard apparatus may be used in place of some of the units illustrated and described. Such and other changes and modifications arebelieved to be within the purview of a person skilled in the art and within the principle of the invention and the scopeof the appended claims.

We claim 1. The method of regulating the fuel supply to a furnace which is supplied by a primary and a secondary fuel supply line each of which is controlled by a valve, which consists in automatlcally closing the secondary control valve in response to a given temperature within the furnace, said secondary controlvalve having been manually opened at the start of the furnace, and thereafter automatically controlling the fuel supply through the primary line only throughout the opera tion of the furnace.

2. The method of regulating the fuel sup.- ply to a furnace which is supplied by a primary and a secondary fuel supply line each of which is controlled by a valve, which consists in automatically closing the secondary control Valve before a iven temperature is reached within the furnace, said secondary control valve having been manually opened at the start of thefurnace, and thereafter automatically controlling the fuel supply through the primary line only throughout the operation of the furnace.

3. The method of regulating the fuel supply to a furnace which is supplied bya primary and a secondary fuel supply line each of which is controlled by a valve, which consists in automatically closing the secondary throughout control valve at a point, automatically adjustable, before a given temperature is reached within the furnace, said secondary control valve having been manually opened at the start of the furnace, and thereafter automatically controlling the fuel supply through the primary line only throughout the operation of the furnace.

4. The method of regulating the fuel supply to a furnace which is supplied by a primary and a secondary fuel supply line each of which is controlled by a valve, which consists in automatically opening the primary control valve and manually opening the secondary control valve at the start of the furnace, automatically closing both valves in response to a given temperature within the furnace and thereafter automatically controlling the fuel supply through the primary line only the operation of the furnace.

5. The method of regulating the fuel supply to a furnace which is supplied by a primary and a secondary fuel supply line each of which is controlled by a valve, which consists in opening both valves at the start of the furnace, automatically closing both valves before a given temperature is reached within the furnace and thereafter automatically controlling the fuel supply through the primary line only throughout the operation of the furnace.

6. The method of regulating the fuel supply to a furnace which is supplied by a primary and a secondary fuel supply line each of which is controlled by a valve, which consists in adjusting said valves for minimum and maximum opening and closing thereof, opening both valves at the start of the furnace, automatically closing both valves before a given temperature is reached within the fur nace and thereafter automatically controlling the fuel supply by operations of the primary valve only throughout the operation of the furnace.

7. The combination of. a furnace, means for supplying fuel thereto, two interconnected valves for controlling said fuel supply and' means for simultaneously closing said valves including means for opening one of said valves without opening the other.

8. The combination of a furnace,a primary and a secondary fuel supply pipe line therefor, a valve means for opening said valves to supply fuel in each of said pipe lines,

to said furnace, automatic means for closing said valves in response to a given temperature mg and closing the primary valve only in recondition within the furnace and forv open- I sponse to variations 1n temperature within the furnace. I

9. The combination of a furnace, a primary and a secondary fuel supply pipe line therefor, a valve in each of said pipe lines, means for opening said valves to supply fuel to said furnace, automatic means for closing in the opposite direction Without causing the by-pass valve to move.

11. The combination of a furnace, a plurality of fuel supply pipes therefor, a valve in each of said pipes, an electric circuit for operating said valves and means in said circuit for causing said valves to close and for automatically operating only one of said valves in response to temperature variations within the furnace.

12. The combination of a furnace, a plurality of fuel supply pipes therefor, a valve in each of said pipes, an electric circuit for operating said valves, means in said circuit for closing said valves when a certain temperature condition exists Within the furnace and for opening and closing one of said valves only in response to variations in temperature within the furnace with respect to the said certain temperature.

13. The combination of a furnace, a main fuel supply pipe and a by-pass fuel supply pipe therefor, a valve in each of said pipes, valve arms for operating the valves, a link. connecting said valve arms to move the same simultaneously in one direction, said link permitting operations of the main valve independent of the by-pass valve and means for operating said link.

'14. The combination of a furnace, means for supplying fuel thereto, valves for regulating the fuel supply, an electric circuit, a motor therein for operating said valves, a device in said circuit operable in response to temperature variations within the furnace,

means in said device for closing an electric circuit through said motor to open only one of said valves at'the start of the furnace, means in said device for closing another circuit through the motor to close both of said valves when a given temperature has been reached within the furnace and other means for making and breaking circuits through the motor in response to further temperature variations within the furnace to operate the said first named valve.

15. The combination of a furnace, means for supplying fuel thereto, valves for regulating the fuel supply, an electric circuit, a motor therein for operating saidvalves, a device in said circuit operable in response to temperature variations within the furnace, 

